;(function(win, lib) {
    var doc = win.document
    var docEl = doc.documentElement
    var metaEl = doc.querySelector('meta[name="viewport"]')
    var flexibleEl = doc.querySelector('meta[name="flexible"]')
    var dpr = 0
    var scale = 0
    var tid
    var flexible = lib.flexible || (lib.flexible = {})
     
    if (metaEl) {
     console.warn('将根据已有的meta标签来设置缩放比例')
     var match = metaEl.getAttribute('content').match(/initial\-scale=([\d\.]+)/)
     if (match) {
      scale = parseFloat(match[1])
      dpr = parseInt(1 / scale)
     }
    } else if (flexibleEl) {
     var content = flexibleEl.getAttribute('content')
     if (content) {
      var initialDpr = content.match(/initial\-dpr=([\d\.]+)/)
      var maximumDpr = content.match(/maximum\-dpr=([\d\.]+)/)
      if (initialDpr) {
       dpr = parseFloat(initialDpr[1])
       scale = parseFloat((1 / dpr).toFixed(2))
      }
      if (maximumDpr) {
       dpr = parseFloat(maximumDpr[1])
       scale = parseFloat((1 / dpr).toFixed(2))
      }
     }
    }
     
    if (!dpr && !scale) {
     var isAndroid = win.navigator.appVersion.match(/android/gi)
     var isIPhone = win.navigator.appVersion.match(/iphone/gi)
     var devicePixelRatio = win.devicePixelRatio
     if (isIPhone) {
      // iOS下，对于2和3的屏，用2倍的方案，其余的用1倍方案
      if (devicePixelRatio >= 3 && (!dpr || dpr >= 3)) {
       dpr = 3
      } else if (devicePixelRatio >= 2 && (!dpr || dpr >= 2)) {
       dpr = 2
      } else {
       dpr = 1
      }
     } else {
      // 其他设备下，仍旧使用1倍的方案
      dpr = 1
     }
     scale = 1 / dpr
    }
     
    docEl.setAttribute('data-dpr', dpr)
    if (!metaEl) {
     metaEl = doc.createElement('meta')
     metaEl.setAttribute('name', 'viewport')
     metaEl.setAttribute(
      'content',
      'initial-scale=' +
       scale +
       ', maximum-scale=' +
       scale +
       ', minimum-scale=' +
       scale +
       ', user-scalable=no'
     )
     if (docEl.firstElementChild) {
      docEl.firstElementChild.appendChild(metaEl)
     } else {
      var wrap = doc.createElement('div')
      wrap.appendChild(metaEl)
      doc.write(wrap.innerHTML)
     }
    }
     
    function refreshRem() {
     var width = docEl.getBoundingClientRect().width
    //  此处进行过修改，屏幕尺寸小于1280px的情况下均可以实现自由缩放
     if (width / dpr > 1440) {
      width = 1440 * dpr
     }
     var rem = width / 10
     docEl.style.fontSize = rem + 'px'
     flexible.rem = win.rem = rem
    }
     
    win.addEventListener(
     'resize',
     function() {
      clearTimeout(tid)
      tid = setTimeout(refreshRem, 300)
     },
     false
    )
    win.addEventListener(
     'pageshow',
     function(e) {
      if (e.persisted) {
       clearTimeout(tid)
       tid = setTimeout(refreshRem, 300)
      }
     },
     false
    )
     
    if (doc.readyState === 'complete') {
     doc.body.style.fontSize = 12 * dpr + 'px'
    } else {
     doc.addEventListener(
      'DOMContentLoaded',
      function(e) {
       doc.body.style.fontSize = 12 * dpr + 'px'
      },
      false
     )
    }
     
    refreshRem()
     
    flexible.dpr = win.dpr = dpr
    flexible.refreshRem = refreshRem
    flexible.rem2px = function(d) {
     var val = parseFloat(d) * this.rem
     if (typeof d === 'string' && d.match(/rem$/)) {
      val += 'px'
     }
     return val
    }
    flexible.px2rem = function(d) {
     var val = parseFloat(d) / this.rem
     if (typeof d === 'string' && d.match(/px$/)) {
      val += 'rem'
     }
     return val
    }
   })(window, window['lib'] || (window['lib'] = {}))